Here's the Chrome guide:

- Open Settings

- Show Advanced Settings (bottom)

- Content Settings (under Privacy)

- Plugins -> "Let me choose when to run content."

- It will now be click-to-play and enable a icon like the pop-up blocker in the address back to enable all on a page or to whitelist the page.

- You can also whitelist from the settings page by clicking Manage Exceptions, and adding them like this: [*.]youtube.com (all sub-domains, and protocols on youtube.com)